Theoretical modelling of ductile damage in duplex stainless steels – Comparison between two micro-mechanical elasto-plastic approaches

► Micro-mechanical models including damage provide very powerful modelling of forming processes. ► Damage coupling with physical phenomenon is done through thermodynamics. ► Damage mechanisms at several scales are taken into account through continuum damage mechanics. ► Two models are compared and exact damage relations are established in both models. ► Numerical aspects are investigates to identify with experimental results in duplex steels. Ductile damage is a consequence of large strains more or less localized inside bands. Taking into account damage in constitutive behaviour of metallic materials is necessary to model various engineering problems involved in forming processes (stamping, punching, shearing…). Damage can be described at macroscopic level with continuum mechanics theories but introducing microstructural features can lead to more accurate predictions. In the present study, two polycrystalline plasticity models including damage effects in the framework of scale transition methods are investigated. These models are based on different approaches with direct application to duplex stainless steel. The first one is a variant of the Lipinski–Berveiller model in which ductile damage effects have been introduced. The second one is a generalized Cailletaud model taking into account ductile damage. Because of the microstructural complexity of the chosen materials, some particular developments of the micro-mechanical approaches are considered. Moreover, continuous damage mechanics is used at grains scale including its coupling with plastic or elastic–plastic flow. The modelling is justified from previous experimental results obtained by neutrons diffraction on duplex stainless steels. The developed models allow then deducing from the grains behaviour the macroscopic behaviour of the aggregate with damage effects.